Permanently energized, brush-type, direct-current motors may be used for operating the pressure supply unit or pressure supply device in electronic brake systems. Examples of electronic brake control systems include an anti-lock braking system (ABS) or an electronic stability control system (electronic stability control, ESP). The motors in the pressure supply unit may have a stator, in which the permanent magnets are situated.
During operation of these brush-type, direct-current motors, electronic interference may be produced by brush sparking or by so-called fritting. This interference may leave the motor via its electric leads. The fritting may be electric current conduction through a commutator boundary layer. During fritting, an electric current is conducted through the very thin, insulating oxide layer of the commutator lamellae. Brush sparking may occur due to current chopping during the commutation operation. The high current gradients associated with this, as well as the fritting, generate electromagnetic interference.
It may be necessary to render interference suppression possible in a high frequency range.